Etymology and synonyms

The word faeces is the plural of the Latin word faex meaning "dregs". In most English-language usage, there is no singular form, making the word a plurale tantum;[1] out of various major dictionaries, only one enters variation from plural agreement.[2] The word is used more in biology and medicine than in other fields (reflecting science's tradition of classical Latin and New Latin); for example, in hunting and tracking, terms such as dung, scat, spoor, and droppings normally are used to refer to non-human animal feces, and in husbandry and farming, manure is common.

Stool is a common term in reference to human feces. For example, in medicine, to diagnose the presence or absence of a medical condition, a stool sample sometimes is requested for testing purposes.[3] In this use, the term stool derives from the noun stool of ease or close stool, a piece of furniture enclosing a chamber pot that could be used during the night and closed afterward, awaiting disposal during the day. But despite its origins, the term "stool" is now sometimes used for any feces, including those of non-human species. The term bowel movement(s) (with each movement a defecation event) is also common in health care.

Ecology

Earthworm feces aid in provision of minerals and plant nutrients in an accessible form

After an animal has digested eaten material, the remains of that material are discharged from its body as waste. Although it is lower in energy than the food from which it is derived, feces may retain a large amount of energy, often 50% of that of the original food.[4] This means that of all food eaten, a significant amount of energy remains for the decomposers of ecosystems. Many organisms feed on feces, from bacteria to fungi to insects such as dung beetles, who can sense odors from long distances.[5] Some may specialize in feces, while others may eat other foods as well. Feces serve not only as a basic food, but also as a supplement to the usual diet of some animals. This is known as coprophagia, and occurs in various animal species such as young elephants eating the feces of their mothers in order to gain essential gut flora, or by other animals such as dogs, rabbits, and monkeys.

Seeds also may be found in feces. Animals who eat fruit are known as frugivores. An advantage for a plant in having fruit is that animals will eat the fruit and unknowingly disperse the seed in doing so. This mode of seed dispersal is highly successful, as seeds dispersed around the base of a plant are unlikely to succeed and often are subject to heavy predation. Provided the seed can withstand the pathway through the digestive system, it is not only likely to be far away from the parent plant, but is even provided with its own fertilizer.

Organisms that subsist on dead organic matter or detritus are known as detritivores, and play an important role in ecosystems by recycling organic matter back into a simpler form that plants and other autotrophs may absorb once again. This cycling of matter is known as the biogeochemical cycle. To maintain nutrients in soil it is therefore important that feces return to the area from which they came, which is not always the case in human society where food may be transported from rural areas to urban populations and then feces disposed of into a river or sea.

Human feces

In humans and depending on the individual and the circumstances, defecation may occur from once every two or three days to several times a day. Extensive hardening of the feces may cause prolonged interruption in the routine and is called constipation.

Human fecal matter varies significantly in appearance, depending on diet and health.[7] Normally it is semisolid, with a mucus coating. The brown coloration comes from a combination of bile and bilirubin, which comes from dead red blood cells.

In newborn babies, initially fecal matter is yellow-green after the meconium. This coloration comes from the presence of bile alone. In time, as the body starts expelling bilirubin from dead red blood cells, it acquires its familiar brown appearance, unless the baby is breast feeding, in which case it remains soft, pale yellowish, and not completely malodorous, until the baby begins to eat significant amounts of other food.

Throughout the life of an ordinary human, one may experience many types of feces. A "green" stool is from rapid transit of feces through the intestines (or the consumption of certain blue or green food dyes in quantity), and "clay-like" appearance to the feces is the result of a lack of bilirubin.

Bile overload is very rare, and not a health threat. Problems as simple as serious diarrhea may cause blood in one's stool. Black stools caused by the presence of blood usually indicate a problem in the intestines (the black color is a sign of digested blood), whereas red streaks of blood in stool usually are caused by bleeding in the rectum or anus.

Sometimes food may make an appearance in the feces. Common undigested foods found in human feces are seeds, nuts, corn, and beans, mainly because of their high dietary fiber content. Beets may turn feces different hues of red. Artificial food coloring in some processed foods, such as highly colorful packaged breakfast cereals, can cause unusual coloring of feces if eaten in sufficient quantities.

Clinical laboratory examination of feces, usually termed as stool examination or stool test, is conducted for the sake of diagnosis, for example, to detect the presence of parasites such as pinworms and their eggs (ova) or, to detect disease spreading bacteria. A stool culture — the controlled growth of microbial organisms in culture media under laboratory conditions — sometimes is performed to identify specific pathogens in stool. The stool guaiac test (or guaiac fecal occult blood test) is conducted to detect the presence of blood in stool that is not apparent to the unaided eye.

Fecal bacteriotherapy — also known as a fecal transplant — is a medical procedure wherein fecal bacteria are transplanted from a healthy individual into a patient.[8][9] Recent research indicates that this may be a valuable method to reestablish normal gut cultures that have been destroyed through the use of antibiotics or some other medical treatments.

Human feces collected for a specific practical use, such as for application as fertilizer, is known as night soil.

Odor

The distinctive odor of feces is due to bacterial action. Gut flora produce compounds such as indole, skatole, and thiols (sulfur-containing compounds), as well as the inorganic gas hydrogen sulfide. These are the same compounds that are responsible for the odor of flatulence. Consumption of foods prepared with spices may result in the spices being undigested and adding to the odor of feces.

The perceived bad odor of feces has been hypothesized to be a deterrent for humans, as consuming or touching it may result in sickness or infection.[10] Human perception of the odor may be contrasted by a non-human animal's perception of it; for example, an animal who eats feces may be attracted to its odor.

Pets

Pets can be trained to use litter boxes or wait to be allowed outside to defecate. Training can be done in several ways, especially dependent on species. An example is crate training for dogs. Several companies market cleaning products for pet owners whose pets have soiled carpets in the home.

Fecal transplant, got flora transplant

In humans, fecal transplants (or stool transplant) is the process of transplantation of fecal bacteria from a healthy individual into a recipient who is suffering from a certain disease, such as irritable bowel syndrome.

Elephants, Hippos, Koalas, and Pandas are born with sterile intestines, and require bacteria obtained from eating the feces of their mothers to digest vegetation.[16]

Coprolites and Paleofeces

A coprolite is fossilized feces and is classified as a trace fossil. In paleontology they give evidence about the diet of an animal. They were first described by William Buckland in 1829. Prior to this they were known as "fossil fir cones" and "bezoar stones". They serve a valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms.[17] Coprolites may range in size from a few millimetres to more than 60 centimetres.

Paleofeces are ancient human feces, often found as part of archaeological excavations or surveys. Intact feces of ancient people may be found in caves in arid climates and in other locations with suitable preservation conditions. These are studied to determine the diet and health of the people who produced them through the analysis of seeds, small bones, and parasite eggs found inside. These feces may contain information about the person excreting the material as well as information about the material. They also may be analyzed chemically for more in-depth information on the individual who excreted them, using lipid analysis and ancient DNA analysis. The success rate of usable DNA extraction is relatively high in paleofeces, making it more reliable than skeletal DNA retrieval.[18]

The reason this analysis is possible at all is due to the digestive system not being entirely efficient, in the sense that not everything that passes through the digestive system is destroyed. Not all of the surviving material is recognizable, but some of it is. Generally, this material is the best indicator archaeologists can use to determine ancient diets, as no other part of the archaeological record is so direct an indicator.[19]

A process that preserves feces in a way that they may be analyzed later is called the Maillard reaction. This reaction creates a casing of sugar that preserves the feces from the elements. To extract and analyze the information contained within, researchers generally have to freeze the feces and grind it up into powder for analysis.[20]

Dog feces were used in the tanning process of leather during the Victorian era. Collected dog feces were mixed with water to form a substance known as "bate." Enzymes in the dog feces helped to relax the fibrous structure of the hide before the final stages of tanning.[24]

Mycobacterium vaccae is a potentially beneficial mind-altering bacteria,[25] which initially was isolated from cow dung.

Social implications

In all human cultures, feces elicit varying degrees of disgust, a basic human emotion. Disgust is experienced primarily in relation to the sense of taste (either perceived or imagined) and, secondarily to anything that causes a similar feeling by sense of smell, touch, or vision. As such, human feces is regarded as something to be avoided diligently: expelled in private and disposed of immediately and without a trace. It often is considered an unacceptable topic in polite conversation and its mere mention may cause offence in certain contexts. An example from the ancient world of the repulsion people have felt toward feces is found in Deuteronomy 23:12-14.

12Designate a place outside the camp where you can go to relieve yourself. 13 As part of your equipment have something to dig with, and when you relieve yourself, dig a hole and cover up your excrement. 14 For the LORD your God moves about in your camp to protect you and to deliver your enemies to you. Your camp must be holy, so that he will not see among you anything indecent and turn away from you.[26]

The disposal of feces always has been associated with the lowest people among a society, the social outcasts, the pariahs, and the social discards. The Caste system in India was created along the lines of profession and the dalits (untouchables) were left to do work related to human emissions. They did such work as cleaning and picking feces from streets, cleaning toilets, and working with dead bodies. Such practices are prevalent even today in the rural and small villages of India.